1. Field of the Invention
The present invention relates to a method for power management in a computer system, and more particularly, to a method for PCI (Peripheral Component Interconnect) Express PM (Power Management) using a PCI PM mechanism in a computer system.
2. Description of the Prior Art
According to the PCI (Peripheral Component Interconnect) Express specification for power management of a computer system, a device can use a Beacon signal (a signal of the Physical Layer) to notify the computer system to recover the main power and then use a PM_PME packet (a packet of the Transaction Layer) to request the computer system to generate an interrupt to awaken the computer system from a non-working mode (such as a standby mode or a sleeping mode). The generated interrupt is similar to the PME (Power Management Event) interrupt defined by the PCI specification. Through the interrupt defined by the PCI Express specification, the computer system is not only PCI Express-compliant but also PCI-compliant.
It is expensive to include a PCI Express wakening mechanism, which is similar to a well-known PCI PME controller, when needed to implement a computer system complying with both the PCI Express specification and the PCI specification. Moreover, some software and hardware conflicts (such as conflicting ACPI event reports and conflicting power-on sequences) between the PCI Express specification and the PCI specification exist if original microchips are used for reducing the production cost. Therefore, a cost-effective method is needed to handle the power management of the computer system.